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Diffstat (limited to 'absl/debugging/internal/stacktrace_x86-inl.inc')
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1 files changed, 327 insertions, 0 deletions
diff --git a/absl/debugging/internal/stacktrace_x86-inl.inc b/absl/debugging/internal/stacktrace_x86-inl.inc new file mode 100644 index 000000000000..6e1af017878e --- /dev/null +++ b/absl/debugging/internal/stacktrace_x86-inl.inc @@ -0,0 +1,327 @@ +// Copyright 2017 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// Produce stack trace + +#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_ +#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_ + +#if defined(__linux__) && (defined(__i386__) || defined(__x86_64__)) +#include <ucontext.h> // for ucontext_t +#endif + +#if !defined(_WIN32) +#include <unistd.h> +#endif + +#include <cassert> +#include <cstdint> + +#include "absl/base/macros.h" +#include "absl/base/port.h" +#include "absl/debugging/internal/address_is_readable.h" +#include "absl/debugging/internal/vdso_support.h" // a no-op on non-elf or non-glibc systems +#include "absl/debugging/stacktrace.h" +#include "absl/base/internal/raw_logging.h" + +#if defined(__linux__) && defined(__i386__) +// Count "push %reg" instructions in VDSO __kernel_vsyscall(), +// preceeding "syscall" or "sysenter". +// If __kernel_vsyscall uses frame pointer, answer 0. +// +// kMaxBytes tells how many instruction bytes of __kernel_vsyscall +// to analyze before giving up. Up to kMaxBytes+1 bytes of +// instructions could be accessed. +// +// Here are known __kernel_vsyscall instruction sequences: +// +// SYSENTER (linux-2.6.26/arch/x86/vdso/vdso32/sysenter.S). +// Used on Intel. +// 0xffffe400 <__kernel_vsyscall+0>: push %ecx +// 0xffffe401 <__kernel_vsyscall+1>: push %edx +// 0xffffe402 <__kernel_vsyscall+2>: push %ebp +// 0xffffe403 <__kernel_vsyscall+3>: mov %esp,%ebp +// 0xffffe405 <__kernel_vsyscall+5>: sysenter +// +// SYSCALL (see linux-2.6.26/arch/x86/vdso/vdso32/syscall.S). +// Used on AMD. +// 0xffffe400 <__kernel_vsyscall+0>: push %ebp +// 0xffffe401 <__kernel_vsyscall+1>: mov %ecx,%ebp +// 0xffffe403 <__kernel_vsyscall+3>: syscall +// + +// The sequence below isn't actually expected in Google fleet, +// here only for completeness. Remove this comment from OSS release. + +// i386 (see linux-2.6.26/arch/x86/vdso/vdso32/int80.S) +// 0xffffe400 <__kernel_vsyscall+0>: int $0x80 +// 0xffffe401 <__kernel_vsyscall+1>: ret +// +static const int kMaxBytes = 10; + +// We use assert()s instead of DCHECK()s -- this is too low level +// for DCHECK(). + +static int CountPushInstructions(const unsigned char *const addr) { + int result = 0; + for (int i = 0; i < kMaxBytes; ++i) { + if (addr[i] == 0x89) { + // "mov reg,reg" + if (addr[i + 1] == 0xE5) { + // Found "mov %esp,%ebp". + return 0; + } + ++i; // Skip register encoding byte. + } else if (addr[i] == 0x0F && + (addr[i + 1] == 0x34 || addr[i + 1] == 0x05)) { + // Found "sysenter" or "syscall". + return result; + } else if ((addr[i] & 0xF0) == 0x50) { + // Found "push %reg". + ++result; + } else if (addr[i] == 0xCD && addr[i + 1] == 0x80) { + // Found "int $0x80" + assert(result == 0); + return 0; + } else { + // Unexpected instruction. + assert(false && "unexpected instruction in __kernel_vsyscall"); + return 0; + } + } + // Unexpected: didn't find SYSENTER or SYSCALL in + // [__kernel_vsyscall, __kernel_vsyscall + kMaxBytes) interval. + assert(false && "did not find SYSENTER or SYSCALL in __kernel_vsyscall"); + return 0; +} +#endif + +// Assume stack frames larger than 100,000 bytes are bogus. +static const int kMaxFrameBytes = 100000; + +// Returns the stack frame pointer from signal context, 0 if unknown. +// vuc is a ucontext_t *. We use void* to avoid the use +// of ucontext_t on non-POSIX systems. +static uintptr_t GetFP(const void *vuc) { +#if defined(__linux__) + if (vuc != nullptr) { + auto *uc = reinterpret_cast<const ucontext_t *>(vuc); +#if defined(__i386__) + const auto bp = uc->uc_mcontext.gregs[REG_EBP]; + const auto sp = uc->uc_mcontext.gregs[REG_ESP]; +#elif defined(__x86_64__) + const auto bp = uc->uc_mcontext.gregs[REG_RBP]; + const auto sp = uc->uc_mcontext.gregs[REG_RSP]; +#else + const uintptr_t bp = 0; + const uintptr_t sp = 0; +#endif + // Sanity-check that the base pointer is valid. It should be as long as + // SHRINK_WRAP_FRAME_POINTER is not set, but it's possible that some code in + // the process is compiled with --copt=-fomit-frame-pointer or + // --copt=-momit-leaf-frame-pointer. + // + // TODO(bcmills): -momit-leaf-frame-pointer is currently the default + // behavior when building with clang. Talk to the C++ toolchain team about + // fixing that. + if (bp >= sp && bp - sp <= kMaxFrameBytes) return bp; + + // If bp isn't a plausible frame pointer, return the stack pointer instead. + // If we're lucky, it points to the start of a stack frame; otherwise, we'll + // get one frame of garbage in the stack trace and fail the sanity check on + // the next iteration. + return sp; + } +#endif + return 0; +} + +// Given a pointer to a stack frame, locate and return the calling +// stackframe, or return null if no stackframe can be found. Perform sanity +// checks (the strictness of which is controlled by the boolean parameter +// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned. +template <bool STRICT_UNWINDING, bool WITH_CONTEXT> +ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS // May read random elements from stack. +ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY // May read random elements from stack. +static void **NextStackFrame(void **old_fp, const void *uc) { + void **new_fp = (void **)*old_fp; + +#if defined(__linux__) && defined(__i386__) + if (WITH_CONTEXT && uc != nullptr) { + // How many "push %reg" instructions are there at __kernel_vsyscall? + // This is constant for a given kernel and processor, so compute + // it only once. + static int num_push_instructions = -1; // Sentinel: not computed yet. + // Initialize with sentinel value: __kernel_rt_sigreturn can not possibly + // be there. + static const unsigned char *kernel_rt_sigreturn_address = nullptr; + static const unsigned char *kernel_vsyscall_address = nullptr; + if (num_push_instructions == -1) { + absl::debug_internal::VDSOSupport vdso; + if (vdso.IsPresent()) { + absl::debug_internal::VDSOSupport::SymbolInfo + rt_sigreturn_symbol_info; + absl::debug_internal::VDSOSupport::SymbolInfo vsyscall_symbol_info; + if (!vdso.LookupSymbol("__kernel_rt_sigreturn", "LINUX_2.5", STT_FUNC, + &rt_sigreturn_symbol_info) || + !vdso.LookupSymbol("__kernel_vsyscall", "LINUX_2.5", STT_FUNC, + &vsyscall_symbol_info) || + rt_sigreturn_symbol_info.address == nullptr || + vsyscall_symbol_info.address == nullptr) { + // Unexpected: 32-bit VDSO is present, yet one of the expected + // symbols is missing or null. + assert(false && "VDSO is present, but doesn't have expected symbols"); + num_push_instructions = 0; + } else { + kernel_rt_sigreturn_address = + reinterpret_cast<const unsigned char *>( + rt_sigreturn_symbol_info.address); + kernel_vsyscall_address = + reinterpret_cast<const unsigned char *>( + vsyscall_symbol_info.address); + num_push_instructions = + CountPushInstructions(kernel_vsyscall_address); + } + } else { + num_push_instructions = 0; + } + } + if (num_push_instructions != 0 && kernel_rt_sigreturn_address != nullptr && + old_fp[1] == kernel_rt_sigreturn_address) { + const ucontext_t *ucv = static_cast<const ucontext_t *>(uc); + // This kernel does not use frame pointer in its VDSO code, + // and so %ebp is not suitable for unwinding. + void **const reg_ebp = + reinterpret_cast<void **>(ucv->uc_mcontext.gregs[REG_EBP]); + const unsigned char *const reg_eip = + reinterpret_cast<unsigned char *>(ucv->uc_mcontext.gregs[REG_EIP]); + if (new_fp == reg_ebp && kernel_vsyscall_address <= reg_eip && + reg_eip - kernel_vsyscall_address < kMaxBytes) { + // We "stepped up" to __kernel_vsyscall, but %ebp is not usable. + // Restore from 'ucv' instead. + void **const reg_esp = + reinterpret_cast<void **>(ucv->uc_mcontext.gregs[REG_ESP]); + // Check that alleged %esp is not null and is reasonably aligned. + if (reg_esp && + ((uintptr_t)reg_esp & (sizeof(reg_esp) - 1)) == 0) { + // Check that alleged %esp is actually readable. This is to prevent + // "double fault" in case we hit the first fault due to e.g. stack + // corruption. + void *const reg_esp2 = reg_esp[num_push_instructions - 1]; + if (absl::debug_internal::AddressIsReadable(reg_esp2)) { + // Alleged %esp is readable, use it for further unwinding. + new_fp = reinterpret_cast<void **>(reg_esp2); + } + } + } + } + } +#endif + + const uintptr_t old_fp_u = reinterpret_cast<uintptr_t>(old_fp); + const uintptr_t new_fp_u = reinterpret_cast<uintptr_t>(new_fp); + + // Check that the transition from frame pointer old_fp to frame + // pointer new_fp isn't clearly bogus. Skip the checks if new_fp + // matches the signal context, so that we don't skip out early when + // using an alternate signal stack. + // + // TODO(bcmills): The GetFP call should be completely unnecessary when + // SHRINK_WRAP_FRAME_POINTER is set (because we should be back in the thread's + // stack by this point), but it is empirically still needed (e.g. when the + // stack includes a call to abort). unw_get_reg returns UNW_EBADREG for some + // frames. Figure out why GetValidFrameAddr and/or libunwind isn't doing what + // it's supposed to. + if (STRICT_UNWINDING && + (!WITH_CONTEXT || uc == nullptr || new_fp_u != GetFP(uc))) { + // With the stack growing downwards, older stack frame must be + // at a greater address that the current one. + if (new_fp_u <= old_fp_u) return nullptr; + if (new_fp_u - old_fp_u > kMaxFrameBytes) return nullptr; + } else { + if (new_fp == nullptr) return nullptr; // skip AddressIsReadable() below + // In the non-strict mode, allow discontiguous stack frames. + // (alternate-signal-stacks for example). + if (new_fp == old_fp) return nullptr; + } + + if (new_fp_u & (sizeof(void *) - 1)) return nullptr; +#ifdef __i386__ + // On 32-bit machines, the stack pointer can be very close to + // 0xffffffff, so we explicitly check for a pointer into the + // last two pages in the address space + if (new_fp_u >= 0xffffe000) return nullptr; +#endif +#if !defined(_WIN32) + if (!STRICT_UNWINDING) { + // Lax sanity checks cause a crash in 32-bit tcmalloc/crash_reason_test + // on AMD-based machines with VDSO-enabled kernels. + // Make an extra sanity check to insure new_fp is readable. + // Note: NextStackFrame<false>() is only called while the program + // is already on its last leg, so it's ok to be slow here. + + if (!absl::debug_internal::AddressIsReadable(new_fp)) { + return nullptr; + } + } +#endif + return new_fp; +} + +template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT> +ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS // May read random elements from stack. +ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY // May read random elements from stack. +ABSL_ATTRIBUTE_NOINLINE +static int UnwindImpl(void **result, int *sizes, int max_depth, int skip_count, + const void *ucp, int *min_dropped_frames) { + int n = 0; + void **fp = reinterpret_cast<void **>(__builtin_frame_address(0)); + + while (fp && n < max_depth) { + if (*(fp + 1) == reinterpret_cast<void *>(0)) { + // In 64-bit code, we often see a frame that + // points to itself and has a return address of 0. + break; + } + void **next_fp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(fp, ucp); + if (skip_count > 0) { + skip_count--; + } else { + result[n] = *(fp + 1); + if (IS_STACK_FRAMES) { + if (next_fp > fp) { + sizes[n] = (uintptr_t)next_fp - (uintptr_t)fp; + } else { + // A frame-size of 0 is used to indicate unknown frame size. + sizes[n] = 0; + } + } + n++; + } + fp = next_fp; + } + if (min_dropped_frames != nullptr) { + // Implementation detail: we clamp the max of frames we are willing to + // count, so as not to spend too much time in the loop below. + const int kMaxUnwind = 1000; + int j = 0; + for (; fp != nullptr && j < kMaxUnwind; j++) { + fp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(fp, ucp); + } + *min_dropped_frames = j; + } + return n; +} + +#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_ |